The present invention relates to a scroll-type fluid machine which is suitable for use as a compressor of a refrigerating or air-conditioning system. More particularly, the invention is concerned with scroll members incorporated in a scroll-type fluid machine of the type mentioned above and improved to ensure a higher productivity and a higher reliability of operation. The present invention is also concerned with a method for manufacturing the improved scroll members.
A scroll-type fluid machine has been known which incorporates a metallic stationary scroll member having an end wall and a spiral wrap formed on one side of the end wall to protrude upright therefrom, and a metallic orbiting scroll member having an end wall and a spiral wrap protruding upright from one side of the end wall and of the same shape as that of the stationary scroll member but wound in the direction opposite to that in the stationary scroll member, the stationary and orbiting scroll members being assembled together such that the wraps of both members mesh with each other so as to define working chambers therebetween. When this fluid machine is used as a compressor, the orbiting scroll member is power-driven so as to make an orbital motion with respect to the stationary scroll member so that the working chambers are gradually moved towards the center of the stationary scroll member while progressively decreasing their volumes.
In this type of fluid machine, it is necessary that the wraps of both scroll members be machined and finished to a high degree of dimensional precision. This in turn requires a large number of steps in the production process, resulting in a long production time and a low productivity.
In order to obviate these problems, Japanese Unexamined Patent Publication Nos. 91388/1983 and 218382/1984 propose a method in which the orbiting scroll member and the stationary scroll member are both coated at their opposing surfaces with precision-molded resin coating layers. These pieces of literatures, however, merely state that a thermosetting resin, for example, can be suitably used as the material of the coating layers, and fail to disclose practical examples of materials and compositions of the resin coating layers which would exhibit high dimensional precision, wear resistance, fatigue strength and adhesive strength to the metallic material from which the scroll base members are made. In addition, no consideration has been made in the proposal as to the resistance of the resin material to the mixture of a machine oil and the working fluid such as freon. These pieces of literatures also lack any suggestion as to the method of forming the resin coating layers with high dimensional precision and surface accuracy of the wraps, although they mention insert molding employing two-color injection molding technique.
Another problem encountered by the conventional scroll wraps is that, since the wraps have a uniform thickness (dimension measured in the radial direction), over the entire length thereof, the volume in the working chamber cannot be reduced to zero and a dead space is formed even in the final stage of compression. In consequence, scroll members of large sizes are required for obtaining a desired capacity of the compressor.